There have already been proposals to use a card which bears an integrated circuit to constitute a memory as a payment voucher. Said memory is programmed when it is manufactured so as to represent a sum of money. Banks distribute cards to their customers with values corresponding to sums paid in to the banks by said customers. The cards are designed for use in shops. The user inserts his card in a read-and-debit machine which performs a debit operation corresponding to the purchase.
The operation can be repeated until the credit memorized in the integrated circuits is expended. The card must then be changed. Now, producing such cards sets tricky problems since integrated circuits cannot be immediately incorporated in cards such as presently known credit or bank service cards and further, there are difficulties concerning the output contacts which are to co-operate with the reading machines.
Therefore efforts have also been made to locate such integrated circuits in objects such as rings or fountain-pens where one integrated circuit could be replaced by another when the memory of the circuit has expended all its credit. However, such systems are dangerous since they allow defrauders who manage to obtain copies of integrated circuits to refill the ring or the fountain-pen.